I am confused about the difference between
http://example.com, is that true "www" is actually the subdomain of domain example.com? Do people usually redirect from
http://www.example.com or it is the reverse? Please enlighten me!
It's true that
www is typically a CNAME or PTR record -- it could also be a subdomain, in case there are CNAMEs or PTRs for
I most often see
example.com redirected to
www.example.com, but I prefer the other direction, and publicize my own sites without the
The "www." helps identify a web server, but not all web servers use those letters - as an example, Yahoo has news.yahoo.com, maps.yahoo.com, store.yahoo.com, shopping.yahoo.com, and www.yahoo.com, and probably others - each one is completely different.
www is the host name. Connecting to a domain without a host name is called "the default host". When the world wide web was first set up, www was used as a host name to indicate that the host was part of the world wide web. At some point it became clear that most http requests to public sites simply want to get to the home web page of the organization that hosts the site, so the concept of host is mostly irrelevant, and the concept of a www host is redundant.
This is a matter of personal preference. If you use the default host people don't have to type as much, which is a clear benefit.